1. Field of the Invention
The invention is related to a mobile thick matter pump having a drive mechanism comprising a vehicle motor and a gear box, at least one hydraulic pump for driving the thick matter pump, which pump is adapted to be coupled to a driven shaft of the gear box, if need be under interposition of a transfer gear box, as well as a speed limiter device for setting a maximum motor speed during the operation of the pump.
2. Description of the Related Art
For mobile concrete pumps it is known to use the existing motor and gear box of the vehicle to drive the hydraulic pumps. To this end, a transfer gear box is usually disposed in the drive train of the vehicle, which can be alternatively switched from a driving operation to a pumping operation. During the driving operation the driven shaft of the gear box is connected to the axle drive shafts of the vehicle by way of a direct drive of the gear box, while during the pumping operation it is switched to the hydraulic pumps. In the latter case the ratio of the gear box is chosen such that the maximum allowable pump speed is attained with the gear ratio of the gear box being a direct ratio (i=1) and approximately nominal speed of the motor. In many vehicle gear boxes the direct ratio is at the same time the highest speed ratio of the gear box and therefore corresponds to the highest gear. In principle it is possible to also pump using a lower gear. When limiting the maximum motor speed in the direct ratio to the nominal speed of the motor the maximum speed of the hydraulic pump and therefore the maximum pump capacity is not attained, though. Some vehicle gear boxes also have a speed increasing ratio (overdrive--i&lt;1), in which the speed at the gear box output is higher than the motor speed. This is often realized by an intermediate gear or an additional gear of the gear box and serves as an economy or overdrive gear at high vehicle speeds.
During the operation of the known concrete pumps it is regarded to be disadvantageous that the speed setting in the region of the efficient nominal speed is accompanied by high noise levels and fuel comsumption.